Differences between the Fc receptors of two lymphocyte subpopulations of human peripheral blood

Fc receptor--more answers, more questions

Fc receptors, belonging to the most important surface structures of a number of cells participating in the immune processes, have been intensely studied during the past decade. The present review summarizes the contemporary knowledge of the specificity and heterogeneity of Fc receptors and of factors influencing their expression, and includes some views on their function. In addition, it mentions their relationship to other cell surface structures, expression of Fc receptors during ontogeny of the organism and in certain diseases. Finally, data concerning the isolation and biochemical characterization of the Fc receptor molecule are presented.

Measurement of K cell activity: use of human OR1R1 red cells and anti-D to study the role of different leucocytes as effector cells

A method for quantitative assay of K cell activity (KCA) with an allogenic combination of human OR1R1 red cells and anti-D (IgG, incomplete antibody) as target cells is described. Lymphocytes alone have been shown to cause lysis of these target cells. Fc receptor-bearing lymphocytes appear to be the chief mediators of KCA. This sub-population is a heterogeneous mixture of sub-sets of other sub-populations defined on the basis of different surface markers and likely to show variable expression of Fc receptors by the EA gamma rosette method. Monocytes and neutrophils (and possibly eosinophils), most of which bear Fc receptors, are ineffective as effector cells. Monocytes may in some instances have an inhibitory effect on the expression of KCA of lymphocytes. The method described has the advantage of simplicity (easy availability of OR1R1 cells and anti-D) and a high degree of sensitivity (marked lysis at low L/T ratio) and appears suitable for routine use in clinical practice.

Importance of IgG subclasses of anti-Rh antibodies for the detection of Fc-receptor-bearing human lymphocytes

13 anti-Rh sera were compared for their usefulness in the detection of Fc-receptor-bearing lymphocytes (EAhum test). IgG subclasses of anti-Rh antibodies were determined by the antiglobulin test with monospecific sera and by the detection of Gm allotypic markers in the haemagglutination inhibition test. Six sera with IgG1 + IgG3 or IgG1 + IgG2 + IgG3 antibodies and one with pure IgG3 antibodies were found to be useful, whereas six other sera with only IgG1 were unsuitable for the EAhum test. G3m markers were detected only on the anti-Rh antibodies which were capable of forming rosettes with lymphocytes. The data show that human peripheral lymphocytes possess Fc receptors for IgG3 immunoglobulins.

Studies on the chicken lymphocyte receptor for aggregated IgG

Chicken lymphocytes isolated from different lymphoid organs were analyzed for Fc IgG receptor by binding of heat aggregated IgG (agg IgG) in the indirect immunofluorescence test. The binding of agg IgG was shown to be specific for Fc IgG receptor, since IgM and F(ab')2 fractions were bound to the lymphocytes in a much less degree. The highest frequency of agg IgG binding cells, almost 100%, was found in the bursa of Fabricius. In contrast to bursa, only a small percentage of thymus cells bound agg IgG. Dose-dependent experiments showed that binding of agg IgG to thymus cells takes place only at high concentrations of the aggregates whereas bursa cells bind agg IgG also at low concentrations. The finding indicates the existence of high and low avidity agg IgG receptors and/or different density of Fc receptors on bursa and thymus cells. A far lower percentage of EA rosette forming cells than of agg IgG binding cells in the various lymphoid organs may depend on the existence of two different Fc IgG receptors on the chicken lymphocytes.

Activation of Fc receptor-bearing lymphocytes by immune complexes. II. Killer lymphocytes mediate Fc ligand-induced lymphokine production

Cells that participate in immune complex-induced production of leukocyte migration inhibitory factor (LIF) activity can be concentrated in a population making up 2-4% of human peripheral blood lymphocytes in which greater than 90% of the cells are active in a single cell antibody-dependent cellular cytotoxicity assay. When so concentrated, such killer (K) cell preparations are as efficient in producing LIF activity as mitogen activated T lymphocytes. Other Fc receptor (FcR)-bearing lymphocytes, including natural killer (NK) cells, do not produce measurable LIF activity when incubated with immune complexes (additional evidence that the K and NK cells among ligands to the FcR of the appropriate lymphocytes, possibly without need for exogenous receptor bridging, is the only requirement for their activation to immune complex-induced lymphokine production (ICLP). It is probable that ICLP by K cells palays a role in antibody-mediated effector functions in vivo.

A comparison of EA-Rosette formation on lymphocytes using rabbit and human sensitizing antibodies

The IgG receptors of peripheral blood lymphocytes were studied to determine whether those detected by a rabbit anti-ox erythrocyte antibody (EARa) and a human anti-human erythrocyte antibody (EAHu) were the same. With cells separated by Ficoll-Hypaque and freed of adherent cells by exposure to plastic surfaces, both EA systems gave similar numbers of rosettes. Mixed rosetting occurred when both types of sensitized cells were added simultaneously. EAHu and EARa rosettes showed similar kinetics of formation. Depletion of rosette-forming lymphocytes was possible by using both systems, and depletion by one system showed depletion in the other. sIg-bearing lymphocytes were also removed, the amount of depletion being dependent on the degree of RBC sensitization with antibody. EAHu and ERRa rosettes were equally inhibited by IgG of a given species of subclass. Normal human and rabbit IgG were more inhibitory than bovine or guinea-pig IgG. All of the human subclasses inhibited, but IgG and IgG3 were more inhibitory than IgG and IgG4. These results indicate that Fc gamma receptors on human lymphocytes react with an IgG configuration that is present on IgG of many species, although it is variably expressed among them. Human IgG1 and rabbit IgG are equivalent in the system and can be used equally well to detect Fc IgG-receptor-bearing cells.

Lymphocytes bearing Fc gamma receptors in rheumatoid arthritis. I. An increased subpopulation of cells in rheumatoid arthritis detected with Facb rosettes

The chronic production of IgM and IgG antiglobulins is a major feature of rheumatoid arthritis. This implies an abnormal interaction between rheumatoid leucocytes and IgG. A novel rosette assay employing rabbit Facb-coated calf red blood cells has been developed to study receptors for IgG on peripheral blood lymphocytes. Cells were obtained from groups of patients with rheumatoid arthritis (RA), osteoarthritis (OA), ankylosing spondylitis (AS), and healthy control subjects. Receptors for Facb were found on an increased proportion of lymphocytes from RA patients compared with the other groups tested. It has been shown that the Facb rosette assay detects a subpopulation of lymphocytes bearing receptors for the Fc region of IgG. This receptor is clearly capable of recognising and binding only the C gamma 2 domain within the Fc region. As such it shows different specificity from some other Fc receptors detected on mononuclear cells. The number of Facb rosette-forming lymphocytes in an individual sample correlated well with the number of cells bearing 'high avidity' Fc receptors. However, the incidence of these cells in RA patients could not be correlated with disease activity, disease duration, or levels of IgM and IgG rheumatoid factor. Thus increased Facb rosette cells may represent a fundamental imbalance of the immune response in patients with rheumatoid arthritis.

Screening tests for cell-mediated immunodeficiency diseases

As our knowledge of immunology has become more sophisticated we have had to alter our ideas of the etiology of many immune deficiency diseases. Indeed, current concepts now prevalent have led to reclassification of a number of disease entities. In order to keep our diagnostic efforts abreast of the information being generated by the extensive immunology research programs now in progress, the clinical laboratory has been required to offer a new array of sophisticated tests on a relatively routine basis. This article is intended to serve as a brief review of immunobiology and immunodeficiency diseases with an indepth coverage of specialized tests generally available at the large centers. With an understanding of the principles, procedures, and pitfalls of the tests carried out the laboratory scientist is in a better position to assist the clinician in reaching the correct diagnosis. The detailed review is concerned with methods available to separate, classify, and subclassify lymphocytes and thereby allow a categorization of immune deficiency diseases. Toward that end there is a discussion of surface markers, rosetting, mitogenic and antigenic responsiveness as well as lymphokine production. With a view to present day research tests that might eventually find their way into the armamentarium of the clinical laboratory in the future, there is brief discussion of the methods presently used to classify T-cells as helper, suppressor, or effector cells, assays of some of the lymphokines, and measurement of antibody synthesis in cell culture.

Do human B and null lymphocytes form a single immunoglobulin-bearing population?

Human "null" lymphocytes have been recognised because they lack T-lymphocyte membrane markers and the surface membrane immunoglobulin (smIg), detectable by direct immunofluorescence, which conventionally characterises B lymphocytes. But almost all null lymphocytes express smIg determinants which are demonstrable by the direct antiglobulin and mixed antiglobulin rosette tests. It is argued that the definition of a B lymphocyte should be extended to include the null cells which react in these tests. If the heterogeneity of the B-lymphocyte population is more widely recognized, the precise nature of human natural and antibody-dependent killer cells may become clearer.

Surface markers of complement receptor lymphocytes

Normal blood lymphocytes bearing complement receptors (CRL) were divided into two populations, one expressing both CR1 (C4b-C3b receptor) and CR2 (C3d receptor) and a second expressing only CR1. Nearly all of the population that expressed both CR1 and CR2 also bore membrane surface immunoglobulins (Ig) and Ia antigens. The majority of cells that had only CR1 lacked detectable surface Ig. These Ig- CR1+ CR2- cells could be distinguished from the majority of monocytes and immature granulocytes, in that the latter ingested latex particles and expressed CR2 as well as CR1. The Ig- CR1+ cells were further subdivided into an Ia-bearing subpopulation and another that lacked Ia. Among the Ig- Ia- CR1+ cells, one third formed spontaneous rosettes with sheep erythrocytes while all of the remaining CRL were erythrocyte-rosette negative. Essentially all CRL in normal blood had IgG Fc receptors, but a qualitative heterogeneity in the Fc receptors of Ia+ CRL vs. Ia- CRL was observed in their binding of different immune complex systems.